Today the Tour enters its final phase with the first of two gruelling Alpine stages that should finally put daylight between the race's frontrunners.

In circumstances unparalleled in recent history, the top six of the classification are separated by a mere 49 seconds, meaning everything is there for the taking.

Two unclassified climbs on Tuesday - including the 27km hike up the highest pass in the Alps, the Cime de la Bonette - will be followed by the iconic blue riband stage to Alpe d'Huez, with its out-of-category ascents of the Galibier and Croix de la Fer before the legendary 21-hairpinned finale.

Only then will the top riders know whether or not they carry a decent enough cushion into Saturday's deciding 53km time trial from Cerilly to Saint Armand Montrond to begin dreaming of the podium in Paris.

Frank Schleck (LUX/CSC)

Aim: The 28-year-old whippet-like Luxembourger needs to build up as big a gap as possible in the remaining mountain stages over time trial specialists Cadel Evans and Denis Menchov.

What he could do with: The continued excellence of his explosive team CSC. Bjarne Riis' well-oiled machine has firmly controlled the race for the past week, attacking whenever possible and in numbers. Every stage has been a team time trial for CSC as they seek to exploit the obvious weaknesses of Rabobank and Silence-Lotto.

Weaknesses: Paradoxically, the strength of his team. CSC have no clear leader and at some point the Tour ambitions of Carlos Sastre and Schleck must come into conflict.

Prospects: Schleck has ridden a superb Tour but he has - more than metaphorically - a mountain to climb if he is going to win in Paris. A repeat of his 2006 win atop Alpe d'Huez is unlikely given the race situation, but the 28-year-old will be more concerned with gaining much-needed minutes than taking the spoils. In the previous 29.5km time trial at Cholethe, he lost 1'47" to Evans - and on Saturday, the ITT is a 23km longer.

Prediction: 4th

Bernhard Kohl (AUT/Gerolsteiner) +7

Aim: Arguably the biggest surprise of this Tour thus far, the little-known Austrian may be his country's 2006 national road race champion, but that is not saying much. An expert climber, the 26-year-old has ridden into contention through quiet consistency over the first two weeks.

What he could do with: Besides a stronger team, Kohl could do with more belief for even he must be surprised with the level of his performances. If he is to be taken seriously, the current king of the mountains must attack all the way between here and the summit of Alpe d'Huez.

Weaknesses: Time trialing and inexperience.

Prospects: Realistically needs a miracle if he is going to win this Tour, but the podium and polka dot jersey are not out of the question.

Prediction: 6th

Cadel Evans (AUS/Silence-Lotto) +8

Aim: The same as it was six months ago: win the Tour. Losing the yellow jersey must have sowed a little doubt in the animated Australian's mind, but he limited his losses and knows that even if he leaves the Alps without the fabled maillot jaune, given his superiority against the clock, he will remain a strong favourite - provided he holds in over the next two days.

What he could do with: Yaroslav Popovych doing his job and providing him some elusive support in the mountains. Popo's former Discovery team-mate Lance Armstrong, the seven-time Tour winner, tipped the Ukrainian as a future champion. His form since joining Silence-Lotto suggests otherwise.

Weaknesses: His team and his emotions. Evans is riding alone and is beginning to feel and act like a victim. His tears on taking a career-first yellow jersey betrayed his fragility while his hard-done-by routine comes across as a little pathetic.

Prospects: It's tricky to call. The 31-year-old is probably the most complete rider of the six, if the most unlikely to dazzle. Providing he keeps a strong head, it's his race to lose. But there is a suspicion that Evans is an accident waiting to happen.

Prediction: 2nd

Denis Menchov (RUS/Rabobank) +38

Aim: His whole season has been geared up to winning the Tour and the experienced Russian is perfectly poised to do so. Traditionally stronger in his second major tour of the season, Menchov, 30, is hitting his peak now after a solid Giro in May. Perhaps only an unfortunate slip on the wet road to Prato Nevoso stopped the double Vuelta winner - and not Schleck - seize Evans' yellow jersey on Sunday.

What he could do with: More of the same. Menchov quietly went about his business in the first 10 days of the race but was unfortunate to lose 38 seconds on stage 4 after cross winds and a crash split the peloton. Without that loss, he would now be in yellow. In the mountains he has been stronger than his principal rival Evans, and has shown he has the legs - but maybe not the balance - to attack.

Weaknesses: Like Evans he will have to do it alone, his Rabobank team not ideally suited to sticking with him at altitude. It remains to be seen how much damage he did to his knee during Sunday's fall.

Prospects: With his experience, self-belief, time trialing (he only lost 7" to Evans in Cholet) and form, Menchov is arguably the favourite to enter Paris in yellow.

Prediction: 1st

Christian Vandevelde (USA/Garmin-Chipotle) +39

Aim: The oldest rider amongst the top six, the 32-year-old from Illinois will have his work cut out merely hanging in there. A former team-mate of Armstrong at US Postal, Vandevelde will be targeting a top-five finish in Paris, knowing that anything better would amount to overachievement. Holds an advantage in having ridden with CSC for two years - as such, he knows the Schleck brothers and Sastre inside out.

What he could do with: Like any rider not wearing the colours of CSC, he could do with greater support on the high roads.

Weaknesses: Having been a domestique throughout his career, whether or not the American has the mentality of a team leader and potential winner is open to debate.

Prospects: Vandevelde is strong against the clock but any thoughts of Paris will be dispelled until he sees where he lies in the overall standings following the tribulations of the next two days.

Prediction: 5th

Carlos Sastre (ESP/CSC) +49

Aim: The spotlight might be on the younger Frank Schleck, but the Spaniard can use his five years of extra experience to his benefit. A veteran of seven Tours, Sastre made the podium in 2006 - but only after the Floyd Landis saga. The 33-year-old climber will do anything to actually step on the podium in Paris for the first time, preferably on the top rung - even if it means turning on his team-mate.

What he could do with: Some killer instinct and the hope that Evans experiences a jours sans next Saturday. Also, a Schleck bonk and/or the full backing of his team wouldn't go amiss.

Weaknesses: As with Schleck, the ambiguity of the team leadership might play on his mind. Likewise, his time trialing is suspect, having lost 1'16" to Evans in the last ITT.

Prospects: A bona fide podium finish should befit an excellent talent who just is not enough of an all-round talent to win a major Tour.